The use of sliders in graphical user interfaces is well established. A slider typically comprises a widget that is moved by a user along a track, which may or may not be visible. One common use of a slider in a GUI is as a scroll bar.
The position of the widget within its track determines the content displayed and moving the widget within its track scrolls the content through the display.
The use of a zoom function or a re-size function in GUIs is also well established. Typically the zoom function is available via a menu, hot key, drop-down option or similar. It is therefore difficult to scroll and re-size simultaneously or in very quick succession.
When zoom is used in a GUI that uses a scroll bar the relative size of the widget within its trace changes with the zoom factor. The size of the widget relative to the total length of its track indicates the size of the displayed content relative to the total available content
U.S. Pat. No. 5,553,225 describes a GUI in which the user can change the size of the widget by dragging an edge of the widget and thereby change the zoom factor. Although this mechanism co-locates a mechanism for scrolling and a mechanism for zooming, it has a number of disadvantages. The mechanism is only appropriate to zooming and scrolling and does not have wider application. The mechanism does not allow simultaneous scrolling and zooming. The mechanism would be difficult to use as the direction in which an edge of the widget is dragged to perform a zoom is the same as the direction in which the widget is dragged to perform a scroll, it would therefore be extremely easy to perform a scroll when one intended to perform a zoom and visa versa.